In the off season, pull the relay and fuse that sends 12V to the 7 pin connector. I learned on the F150 forum that having the receptacle powered up all the time with voltage on the pins can accelerate corrosion. My contacts in the the receptacle on my truck still look shiny and new after 3 Michigan winters and I pull the fuse and relay after my final camping trip in the fall.
2006 23B Hybrid with 10k round bar WDH
2011 F150 4x4 SCREW Ecoboost, Max Tow, Integrated TBC, 3.73 LS axle, Firestone Ride Rite airbags.